Chang-Zern Hong

Interrater reliability in myofascial trigger point examination

Abstract The myofascial trigger point (MTrP) is the hallmark physical finding of the myofascial pain syndrome (MPS). The MTrP itself is characterized by distinctive physical features that include a tender point in a taut band of muscle, a local twitch response (LTR) to mechanical stimulation, a pain referral pattern characteristic of trigger points of specific areas in each muscle, and the reproduction of the patients usual pain. No prior study has demonstrated that these physical features are reproducible among different examiners, thereby establishing the reliability of the physical examination in the diagnosis of the MPS. This paper reports an initial attempt to establish the interrater reliability of the trigger point examination that failed, and a second study by the same examiners that included a training period and that successfully established interrater reliability in the diagnosis of the MTrP. The study also showed that the interrater reliability of different features varies, the LTR being the most difficult, and that the interrater reliability of the identification of MTrP features among different muscles also varies.

Pathophysiologic and electrophysiologic mechanisms of myofascial trigger points

OBJECTIVE To review recent clinical and basic science studies on myofascial trigger points (MTrPs) to facilitate a better understanding of the mechanism of an MTrP. DATA SOURCES English literature in the last 15 years regarding scientific investigations on MTrPs in either humans or animals. STUDY SELECTION Research works, especially electrophysiologic studies, related to the pathophysiology of MTrP. DATA SYNTHESIS (1) Studies on an animal model have found that a myofascial trigger spot (MTrS) in a taut band of rabbit skeletal muscle fibers is similar to a human MTrP in many aspects. (2) An MTrP or an MTrS contains multiple minute loci that are closely related to nerve fibers and motor endplates. (3) Both referred pain and local twitch response (characteristics of MTrPs) are related to the spinal cord mechanism. (4) The taut band of skeletal muscle fibers (which contains an MTrP or an MTrS in the endplate zone) is probably related to excessive release of acetylcholine in abnormal endplates. CONCLUSION The pathogenesis of an MTrP appears to be related to integrative mechanisms in the spinal cord in response to sensitized nerve fibers associated with abnormal endplates.

Endplate potentials are common to midfiber myofacial trigger points.

Simons DG, Hong C-Z, Simons LS: Endplate potentials are common to midfiber myofacial trigger points. Am J Phys Med Rehabil 2002;81:212–222. ObjectiveTo compare the prevalence of motor endplate potentials (noise and spikes) in active central myofascial trigger points, endplate zones, and taut bands of skeletal muscle to assess the specificity of endplate potentials to myofascial trigger points. DesignThis nonrandomized, unblinded needle examination of myofascial trigger points compares the prevalence of three forms of endplate potentials at one test site and two control sites in 11 muscles of 10 subjects. The endplate zone was independently determined electrically. Active central myofascial trigger points were identified by spot tenderness in a palpable taut band of muscle, a local twitch response to snapping palpation, and the subject’s recognition of pain elicited by pressure on the tender spot. ResultsEndplate noise without spikes occurred in all 11 muscles at trigger-point sites, in four muscles at endplate zone sites outside of trigger points (P = 0.024), and did not occur in taut band sites outside of an endplate zone (P = 0.000034). ConclusionEndplate noise was significantly more prevalent in myofascial trigger points than in sites that were outside of a trigger point but still within the endplate zone. Endplate noise seems to be characteristic of, but is not restricted to, the region of a myofascial trigger point.

Difference in Pain Relief After Trigger Point Injections in Myofascial Pain Patients With and Without Fibromyalgia

OBJECTIVE To compare responses to trigger point (TrP) injection between patients having both myofascial pain syndrome (MPS) caused by active TrPs and fibromyalgia syndrome (FMS) and patients with MPS due to TrPs but without FMS. DESIGN Prospective design blinded measurement, before- after trial. SETTING A pain control medical clinic. PATIENTS Group 1: MPS + FMS; Group 2: MPS only. All patients (9 in each group) had active TrPs in the upper trapezius muscle. INTERVENTION Myofascial TrP injection with 0.5% xylocaine. MAIN OUTCOME MEASURES Subjective pain intensity (PI), pain threshold (PT), and range of motion (ROM) were assessed before, immediately after, and 2 weeks after TrP injection. RESULTS In a comparison of preinjection measures to immediate postinjection measures, only ROM was significantly improved (p < .05) in Group 1 patients; all three parameters were significantly improved (p < .05) in the Group 2 patients who had only MPS. Two weeks after injection, both groups showed significant improvement (p < .05) in all three measured parameters as compared to preinjection measurements. In a comparison of the two groups, the immediate effectiveness of TrP injection was significantly less (p < .05) in Group 1 than in Group 2 for all three parameters. Two weeks after injection, the degree of improvement in PT or ROM (but not PI) was not significantly different between two groups. Postinjection soreness (different from myofascial pain) was more severe, developed sooner, and lasted longer in Group 1 than in Group 2. CONCLUSION Trigger point injection is a valuable procedure for pain relief for patients in both group. Patients with FMS are likely to experience significant but delayed and attenuated pain relief following injection of their active TrPs compared to myofascial pain patients with similar TrPs but without FMS. Also, FMS patients are likely to experience significantly more postinjection soreness for a longer period of time.

Interexaminer reliability of the palpation of trigger points in the trunk and lower limb muscles

OBJECTIVES To determine the interexaminer reliability of palpation of three characteristics of trigger points (taut band, local twitch response, and referred pain) in patients with subacute low back pain, to determine whether training in palpation would improve reliability, and whether there was a difference between the physiatric and chiropractic physicians. DESIGN Reliability study. SETTING Whittier Health Campus, Los Angeles College of Chiropractic. PARTICIPANTS Twenty-six nonsymptomatic individuals and 26 individuals with subacute low back pain. INTERVENTION Twenty muscles per individual were first palpated by an expert and then randomly by four physician examiners. MAIN OUTCOME MEASURES Palpation findings. RESULTS Kappa scores for palpation of taut bands, local twitch responses, and referred pain were .215, .123, and .342, respectively, between the expert and the trained examiners, and .050, .118, and .326, respectively, between the expert and the untrained examiners. Kappa scores for agreement for palpation of taut bands, twitch responses, and referred pain were .108, -.001, and .435, respectively, among the nonexpert, trained examiners, and -.019, .022, and .320, respectively, among the nonexpert, untrained examiners. CONCLUSIONS Among nonexpert physicians, physiatric or chiropractic, trigger point palpation is not reliable for detecting taut band and local twitch response, and only marginally reliable for referred pain after training.

Dry needling to a key Myofascial trigger point may reduce the irritability of satellite MTrPs

Hsieh Y-L, Kao M-J, Kuan T-S, Chen S-M, Chen J-T, Hong C-Z: Dry needling to a key myofascial trigger point may reduce the irritability of satellite myofascial trigger points. Am J Phys Med Rehabil 2007;86:397–403. Objective:To investigate the changes in pressure pain threshold of the secondary (satellite) myofascial trigger points (MTrPs) after dry needling of a primary (key) active MTrP. Design:Single blinded within-subject design, with the same subjects serving as their own controls (randomized). Fourteen patients with bilateral shoulder pain and active MTrPs in bilateral infraspinatus muscles were involved. An MTrP in the infraspinatus muscle on a randomly selected side was dry needled, and the MTrP on the contralateral side was not (control). Shoulder pain intensity, range of motion (ROM) of shoulder internal rotation, and pressure pain threshold of the MTrPs in the infraspinatus, anterior deltoid, and extensor carpi radialis longus muscles were measured in both sides before and immediately after dry needling. Results:Both active and passive ROM of shoulder internal rotation, and the pressure pain threshold of MTrPs on the treated side, were significantly increased (P < 0.01), and the pain intensity of the treated shoulder was significantly reduced (P < 0.001) after dry needling. However, there were no significant changes in all parameters in the control (untreated) side. Percent changes in the data after needling were also analyzed. For every parameter, the percent change was significantly higher in the treated side than in the control side. Conclusions:This study provides evidence that dry needle–evoked inactivation of a primary (key) MTrP inhibits the activity in satellite MTrPs situated in its zone of pain referral. This supports the concept that activity in a primary MTrP leads to the development of activity in satellite MTrPs and the suggested spinal cord mechanism responsible for this phenomenon.

Effectiveness of four conservative treatments for subacute low back pain: A randomized clinical trial

Study Design. A randomized, assessor-blinded clinical trial was conducted. Objective. To investigate the relative effectiveness of three manual treatments and back school for patients with subacute low back pain. Summary of Background Data. Literature comparing the relative effectiveness of specific therapies for low back pain is limited. Methods. Among the 5925 inquiries, 206 patients met the specific admission criteria, and 200 patients randomly received one of four treatments for 3 weeks: back school, joint manipulation, myofascial therapy, and combined joint manipulation and myofascial therapy. These patients received assessments at baseline, after 3 weeks of therapy, and 6 months after the completion of therapy. The primary outcomes were evaluated using visual analog pain scales and Roland–Morris activity scales. Results. All four groups showed significant improvement in pain and activity scores after 3 weeks of care, but did not show further significant improvement at the 6-month follow-up assessment. No statistically significant between-group differences were found either at the 3-week or 6-month reassessments. Conclusions. For subacute low back pain, combined joint manipulation and myofascial therapy was as effective as joint manipulation or myofascial therapy alone. Additionally, back school was as effective as three manual treatments.

The immediate effectiveness of electrical nerve stimulation and electrical muscle stimulation on myofascial trigger points

This study is designed to investigate the immediate effectiveness of electrotherapy on myofascial trigger points of upper trapezius muscle. Sixty patients (25 males and 35 females) who had myofascial trigger points in one side of the upper trapezius muscles were studied. The involved upper trapezius muscles were treated with three different methods according to a random assignment: group A muscles (n = 18) were given placebo treatment (control group); group B muscles (n = 20) were treated with electrical nerve stimulation (ENS) therapy; and group C muscles (n = 22) were given electrical muscle stimulation (EMS) therapy. The effectiveness of treatment was assessed by conducting three measurements on each muscle before and immediately after treatment: subjective pain intensity [(PI) with a visual analog scale], pressure pain threshold [(PT) with algometry], and range of motion [(ROM) with a goniometer] of upper trapezius muscle (lateral bending of cervical spine to the opposite side). When the effectiveness of treatment was compared with that of the placebo group (group A), there was significant improvement in PI and PT in group B (P < 0.01) but not in group C (P > 0.05). The improvement of ROM was significantly more in group C (P < 0.01) as compared with that in group A or group B. When each group was divided into two additional subgroups based on the initial PI, it was found that ENS could reduce PI and increase PT significantly (P < 0.05), but did not significantly (P > 0.05) improve ROM, as compared with the placebo group for both subgroups. EMS could significantly (P < 0.05) improve ROM, but not PT, better than the placebo groups, for either subgroup. It could reduce PI significantly more (P < 0.05) than placebo controls only for the subgroup with mild to moderate pain, but not with severe pain. For pain relief, ENS was significantly better (P < 0.05) than EMS; but for the improvement of ROM, EMS was significantly better (P < 0.05) than ENS. It is concluded that ENS is more effective for immediate relief of myofascial trigger point pain than EMS, and EMS has a better effect on immediate release of muscle tightness than ENS.

Inhibitory effect of dry needling on the spontaneous electrical activity recorded from myofascial trigger spots of rabbit skeletal muscle.

Chen JT, Chung KC, Hou CR, Kuan CR, Chen SM, Hong CZ: Inhibitory effect of dry needling on the spontaneous electrical activity recorded from myofascial trigger spots of rabbit skeletal muscle. Am J Phys Med Rehabil 2000;80:729–735. Objective: Dry needling of myofascial trigger points can relieve myofascial pain if local twitch responses are elicited during needling. Spontaneous electrical activity (SEA) recorded from an active locus in a myofascial trigger point region has been used to assess the myofascial trigger point sensitivity. This study was to investigate the effect of dry needling on SEA. Design: Nine adult New Zealand rabbits were studied. Dry needling with rapid insertion into multiple sites within the myofascial trigger spot region was performed to the biceps femoris muscle to elicit sufficient local twitch responses. Very slow needle insertion with minimal local twitch response elicitation was conducted to the other biceps femoris muscle for the control study. SEA was recorded from 15 different active loci of the myofascial trigger spot before and immediately after treatment for both sides. The raw data of 1-sec SEA were rectified and integrated to calculate the average integrated value of SEA. Results: Seven of nine rabbits demonstrated significantly lower normalized average integrated value of SEA in the treatment side compared with the control side (P < 0.05). The results of two-way analysis of variance show that the mean of the normalized average integrated value of SEA in the treatment group (0.565 ± 0.113) is significantly (P < 0.05) lower than that of the control (0.983 ± 0.121). Conclusions: Dry needling of the myofascial trigger spot is effective in diminishing SEA if local twitch responses are elicited. The local twitch response elicitation, other than trauma effects of needling, seems to be the primary inhibitory factor on SEA during dry needling.

Remote effects of dry needling on the irritability of the myofascial trigger point in the upper trapezius muscle.

Tsai C-T, Hsieh L-F, Kuan T-S, Kao MJ, Chou L-W, Hong C-Z: Remote effects of dry needling on the irritability of the myofascial trigger point in the upper trapezius muscle. Objective:To investigate the remote effect of dry needling on the irritability of a myofascial trigger point in the upper trapezius muscle. Design:Thirty-five patients with active myofascial trigger points in upper trapezius muscles were randomly divided into two groups: 18 patients in the control group received sham needling, and 17 patients in the dry-needling group received dry needling into the myofascial trigger point in the extensor carpi radialis longus muscle. The subjective pain intensity, pressure pain threshold, and range of motion of the neck were assessed before and immediately after the treatment. Results:Immediately after dry needling in the experimental group, the mean pain intensity was significantly reduced, but the mean pressure threshold and the mean range of motion of cervical spine were significantly increased. There were significantly larger changes in all three parameters of measurement in the dry-needling group than that in the control group. Conclusions:This study demonstrated the remote effectiveness of dry needling. Dry needling of a distal myofascial trigger point can provide a remote effect to reduce the irritability of a proximal myofascial trigger point.